Panel-cooled submerged combustion melter geometry and methods of making molten glass

ABSTRACT

A melter apparatus includes a floor, a ceiling, and a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, a melting zone being defined by the floor, ceiling and wall, the melting zone having a feed inlet and a molten glass outlet positioned at opposing ends of the melting zone. The melting zone includes an expanding zone beginning at the inlet and extending to an intermediate location relative to the opposing ends, and a narrowing zone extending from the intermediate location to the outlet. One or more burners, at least some of which are positioned to direct combustion products into the melting zone under a level of molten glass in the zone, are also provided.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to the field of combustionfurnaces and methods of use, and more specifically to improved submergedcombustion melters and methods of use in producing molten glass.

2. Related Art

Glass melting furnaces have traditionally been of rectangular shape dueto the issue of construction with refractory blocks and ability tocontrol the flow of the molten glass through the melter. (Someall-electric designs are circular, such as Pochet and SORG VSM designs.)However, there are significant dead (low flow or stagnant) regions thatresult from the rectangular construction.

Submerged combustion has been proposed in several patents forapplication in commercial glass melting, including U.S. Pat. Nos.4,539,034; 3,170,781; 3,237,929; 3,260,587; 3,606,825; 3,627,504;3,738,792; 3,764,287; 6,460,376; 6,739,152; 6,857,999; 6,883,349;7,273,583; 7,428,827; 7,448,231; and 7,565,819; and published U.S. Pat.Application numbers 2004/0168474; 2004/0224833; 2007/0212546;2006/0000239; 2002/0162358; 2009/0042709; 2008/0256981; 2007/0122332;2004/0168474; 2004/0224833; and 2007/0212546. In submerged combustionglass melting the combustion gases are injected beneath the surface ofthe molten glass and rise upward through the melt. The glass is heatedat a higher efficiency via the intimate contact with the combustiongases. However, using submerged combustion burners does not alleviatedead flow regions that result from the rectangular construction of themelter itself.

Energy costs continue to increase, spurring efforts to find ways toreduce the amount of fuel in glass manufacturing. Oxy-fuel burners havebeen used in the glass industry in general, especially in thefiberglass, TV glass, and container glass industry segments. There arefew complete oxy-fuel fired float furnaces in operation today and theyhave been using retrofit oxy-fuel burners designed specifically forsmaller container or fiberglass furnaces. These conversions were mostlikely made to meet emissions standards. Known oxy-fuel burners arepredominately nozzle mix designs and avoid premixing for safety reasonsdue to the increased reactivity of using oxygen as the oxidant versusair. Some common designs of nozzle mix oxy-fuel burners are described inU.S. Pat. Nos. 5,199,866; 5,490,775; and 5,449,286. The concept ofnozzle mix oxy-fuel burners is to mix fuel and oxygen at the burnernozzle. The flame produced is a diffusion flame with the flamecharacteristics determined by mixing rates. Short intense flames aremost common with these burners, however some delayed mixing geometry areconsidered to generate longer luminous flames. More recently, “flatflame” burners have been used in the industry for melting applications,in which the flame is above the melt and generally parallel thereto.These burners produce a flame that is 2 to 3 times wider than atraditional (cylindrical) oxy-fuel flame. U.S. Pat. Nos. 5,545,031;5,360,171; 5,299,929; and 5,575,637 show examples of flat flame burners.The above-mentioned U.S. Pat. No. 7,273,583 describes a submergedcombustion burner having co-axial fuel and oxidant tubes forming anannular space therebetween, wherein the outer tube extends beyond theend of the inner tube. A burner nozzle having an outside diametercorresponding to the inside diameter of the outer tube is connected tothe outlet end of the inner tube and forms a centralized opening influid communication with the inner tube and at least one peripherallongitudinally oriented opening in fluid communication with the annularspace. A longitudinally adjustable rod may be disposed within the innertube for adjustment of fluid flow therethrough, and a cylindrical inserthaving a flame stabilizer for stabilizing a flame produced by the burneris attached to the outlet end of the outer tube. All of the patentdocuments referenced in this document are incorporated herein byreference.

It would be an advance in the glass melting art to developnon-rectangular melting furnaces (“melters”) that have reduced dead flow(stagnant) regions, while taking advantage of the efficiency ofsubmerged combustion burners, to increase melter throughput and producehigh quality molten glass.

SUMMARY

In accordance with the present disclosure invention, melters andprocesses of using them are described that reduce dead flow (stagnant)regions and take advantage submerged combustion burners. The melters ofthe present disclosure are at least partially constructed using cooledrefractory panels, which allows construction of melters havingconfigurations that reduce or avoid the dead flow corner regionsprevalent in traditional glass melter rectangular designs by eliminatingthe dead (low or stagnant) corners of the known rectangular melterconfigurations. In certain melter embodiments according to thisdisclosure, the side walls are angled so that the flow spacing formolten glass narrows toward the discharge (molten glass outlet), incertain embodiments to the extreme of a V-shape. In melters taught anddescribed in this disclosure, the molten glass flow can be completelymelted and glass of high quality produced with minimal energy waste.These melter designs are relevant to the full range of materials thatcould be melted with submerged combustion technology. With submergedcombustion technology the use of a cooled panel design is feasible dueto the greatly reduced size of the melter for a given throughput. Theuse of cooled panels (cooled using fluid—liquid, gas, or combinationthereof) to construct a glass melter allows more flexibility in theshape of the melter, especially in combination with submerged combustionburners.

“Submerged” as used herein means that combustion gases emanate fromburners under the level of the molten glass; the burners may befloor-mounted, wall-mounted, or in melter embodiments comprising morethan one submerged combustion burner, any combination thereof (forexample, two floor mounted burners and one wall mounted burner). As usedherein the term “combustion gases” means substantially gaseous mixturesof combusted fuel, any excess oxidant, and combustion products, such asoxides of carbon (such as carbon monoxide, carbon dioxide), oxides ofnitrogen, oxides of sulfur, and water. Combustion products may includeliquids and solids, for example soot and unburned liquid fuels.“Oxidant” as used herein includes air and gases having the same molarconcentration of oxygen as air, oxygen-enriched air (air having oxygenconcentration of oxygen greater than 21 mole percent), and “pure”oxygen, such as industrial grade oxygen, food grade oxygen, andcryogenic oxygen. Oxygen-enriched air may have 50 mole percent or moreoxygen, and in certain embodiments may be 90 mole percent or moreoxygen. Oxidants may be supplied from a pipeline, cylinders, storagefacility, cryogenic air separation unit, membrane permeation separator,or adsorption unit.

A first aspect of the invention is a melter apparatus comprising:

-   -   a) a floor and a ceiling;    -   b) a substantially vertical wall connecting the floor and        ceiling at a perimeter of the floor and ceiling, a melting zone        being defined by the floor, ceiling and wall, the melting zone        having a feed inlet and a molten glass outlet positioned at        opposing ends of the melting zone, the melting zone comprising        an expanding zone beginning at the inlet and extending to an        intermediate location relative to the opposing ends, and a        narrowing zone extending from the intermediate location to the        outlet; and    -   c) a plurality of burners, at least some of which are positioned        to direct combustion products into the melting zone under a        level of molten glass in the zone.

In certain embodiments the intermediate location is positioned where themelting zone has a maximum width W_(M). In certain embodiments at leastsome of the wall comprises fluid-cooled refractory panels. In certainembodiments, the fluid-cooled panels are liquid-cooled panels comprisingone or more passages for flow of a liquid into and out of the passages.

In certain embodiments the melting zone has a plan view shape defined byfirst and second trapezoids sharing a common base positioned at theintermediate location and substantially perpendicular to a longitudinalaxis of the melter, the first trapezoid having a side parallel to thebase and positioned at the inlet, the second trapezoid having a sideparallel to the base and positioned at the outlet.

In certain embodiments at least some of the burners are floor-mountedand positioned in one or more parallel rows substantially perpendicularto a longitudinal axis of the melter. In certain embodiments, the numberof burners in each row is proportional to width of the melter. Incertain embodiments the depth of the melter decreases as width of themelter in the narrowing zone decreases. In certain other embodiments,the intermediate location comprises a constant width zone positionedbetween the expanding zone and the narrowing zone.

In certain embodiments, at least some of the burners are oxy-fuelburners. In certain embodiments the oxy-fuel burners may comprise one ormore submerged combustion burners each having co-axial fuel and oxidanttubes forming an annular space therebetween, wherein the outer tubeextends beyond the end of the inner tube, as taught in U.S. Pat. No.7,273,583.

In certain embodiments, the melter apparatus has a throughput of 2 ft²per short ton per day (2 ft2/stpd) or less, and in some embodiments 0.5ft²/stpd or less.

In certain exemplary embodiments, wherein the melter wall comprisesfluid-cooled panels, the wall comprises a refractory liner at leastbetween the panels and the molten glass.

In certain embodiments the wall in the expanding zone and the narrowingzone is non-linear.

In certain embodiments, the refractory cooled-panels are cooled by aheat transfer fluid selected from the group consisting of gaseous,liquid, or combinations of gaseous and liquid compositions thatfunctions or is capable of being modified to function as a heat transferfluid. Gaseous heat transfer fluids may be selected from air, includingambient air and treated air (for air treated to remove moisture), inertinorganic gases, such as nitrogen, argon, and helium, inert organicgases such as fluoro-, chloro- and chlorofluorocarbons, includingperfluorinated versions, such as tetrafluoromethane, andhexafluoroethane, and tetrafluoroethylene, and the like, and mixtures ofinert gases with small portions of non-inert gases, such as hydrogen.Heat transfer liquids may be selected from inert liquids which may beorganic, inorganic, or some combination thereof, for example, saltsolutions, glycol solutions, oils and the like. Other possible heattransfer fluids include steam (if cooler than the oxygen manifoldtemperature), carbon dioxide, or mixtures thereof with nitrogen. Heattransfer fluids may be compositions comprising both gas and liquidphases, such as the higher chlorofluorocarbons.

Another aspect of this disclosure is a process comprising:

-   -   a) feeding at least one partially vitrifiable material into a        feed inlet of a melting zone of a refractory melter apparatus        comprising a floor, a ceiling, and a substantially vertical wall        connecting the floor and ceiling at a perimeter of the floor and        ceiling, the melting zone comprising an expanding zone beginning        at the inlet and extending to an intermediate location relative        to opposing ends of the melter, and a narrowing zone extending        from the intermediate location to a molten glass outlet;    -   b) heating the at least one partially vitrifiable material with        at least one burner directing combustion products into the        melting zone under a level of the molten glass in the zone; and    -   c) discharging molten glass from a molten glass outlet        positioned at an end of the melting zone opposite the inlet.

In certain embodiments, the process comprises discharging at least 0.5short tons per day per square foot of melter floor, and in certainexemplary processes, at least 2 short tons per day per square foot ofmelter floor.

Certain exemplary processes comprise cooling the wall by the wallcomprising cooled refractory panels and directing a heat transfer fluidthrough the panels.

Certain apparatus embodiments may include a plurality of tubesfunctioning to route oxygen or oxygen-enriched air through a refractoryburner block, the tubes fluidly connected to one or more oxygen supplymanifolds. Both the tubes and the manifolds may be comprised of metal,ceramic, ceramic-lined metal, or combination thereof.

In all apparatus embodiments the sources of oxidant and fuel may be oneor more conduits, pipelines, storage facility, cylinders, or, in thecase of oxidant, ambient air. Secondary and tertiary oxidants, if usedmay be supplied from a pipeline, cylinder, storage facility, cryogenicair separation unit, membrane permeation separator, or adsorption unitsuch as a vacuum swing adsorption unit.

Certain embodiments may comprise using oxygen-enriched air as theprimary oxidant, the fuel is a gaseous fuel, the gaseous fuel beingselected from methane, natural gas, liquefied natural gas, propane,carbon monoxide, hydrogen, steam-reformed natural gas, atomized oil ormixtures thereof, and the oxygen-enriched air comprising at least 90mole percent oxygen. In certain embodiments the oxygen may be injectedinto an intermediate mixture upstream of a combustion chamber of aburner, while in other embodiments the oxygen may be injected into thecombustion chamber. The oxygen injection volumetric flow rate velocitymay range from about be 21000 scfh (standard cubic feet per hour) toabout 8000 scfh (about 28 cubic meters/hour (m³/h) to about 225 m³/h),or from about 2000 scfh to about 6000 scfh (about 56 m³/h to about 168m³/h), with natural gas flow rates ranging from about 1000 scfh to about4000 scfh (about 28 to about 112 m³/h), or from about 1000 to about 3000scfh (about 28 to about 84 m³/h) ft/sec or less at a flow rate rangingfrom 0 to about 6000 scfh, [current sized burners are 2 MMBtu/hr whichis 2000 scfh NG and 4000 scfh Oxygen so 400 very low, do not havenumbers to see if velocity in ballpark] and may be injected through anon-cooled manifold, a gas-cooled manifold, or a liquid-cooled manifold.The gas-cooled manifold may utilize air as a coolant gas, while theliquid-cooled manifold may use water as a coolant. Methods of theinvention include those wherein the combustion chamber pressure does notexceed 10 psig.

Melter apparatus and process embodiments of the invention may becontrolled by one or more controllers. For example, burner combustion(flame) temperature may be controlled by monitoring one or moreparameters selected from velocity of the fuel, velocity of the primaryoxidant, mass and/or volume flow rate of the fuel, mass and/or volumeflow rate of the primary oxidant, energy content of the fuel,temperature of the fuel as it enters the burner, temperature of theprimary oxidant as it enters the burner, temperature of the effluent,pressure of the primary oxidant entering the burner, humidity of theoxidant, burner geometry, combustion ratio, and combinations thereof.Exemplary apparatus and methods of the invention comprise a combustioncontroller which receives one or more input parameters selected fromvelocity of the fuel, velocity of the primary oxidant, mass and/orvolume flow rate of the fuel, mass and/or volume flow rate of theprimary oxidant, energy content of the fuel, temperature of the fuel asit enters the burner, temperature of the primary oxidant as it entersthe burner, pressure of the oxidant entering the burner, humidity of theoxidant, burner geometry, oxidation ratio, temperature of the effluentand combinations thereof, and employs a control algorithm to controlcombustion temperature based on one or more of these input parameters.

Melter apparatus and methods of the invention will become more apparentupon review of the brief description of the drawings, the detaileddescription of the invention, and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the objectives of the invention and other desirablecharacteristics can be obtained is explained in the followingdescription and attached drawings in which:

FIGS. 1-5, inclusive, are plan views, with parts broken away, of fivemelter embodiments in accordance with the present disclosure;

FIG. 6 is a side sectional view of the melter of FIG. 1; and

FIG. 7 is a perspective view of one cooled panel useful in melters ofthe present disclosure.

It is to be noted, however, that the appended drawings are not to scaleand illustrate only typical embodiments of this invention, and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of various melter apparatus and process embodiments inaccordance with the present disclosure. However, it will be understoodby those skilled in the art that the melter apparatus and processes ofusing same may be practiced without these details and that numerousvariations or modifications from the described embodiments may bepossible which are nevertheless considered within the appended claims.

Referring now to the figures, FIGS. 1-5 are plan views, with partsbroken away, of five melter embodiments in accordance with the presentdisclosure. FIG. 6 is a side cross-sectional view of the melterapparatus illustrated in FIG. 1. The same numerals are used for the sameor similar features in the various figures. In the plan viewsillustrated in FIGS. 1-5, it will be understood in each case that theroof and exhaust chimney are not illustrated in order to illustrate moreclearly the key features of each embodiment. Embodiment 100 of FIG. 1comprises a peripheral wall 2 of melter 100, wall 2 having an inlet 4, abatch feed chute 5, and a melter discharge 6 through which molten glassexits the melter. Melter 100 also comprises a roof 7 (FIG. 6), a floor8, a feed end 9, and a discharge end 11.

An important feature of all melter apparatus described herein, andexemplified in melter 100 of FIG. 1, is that wall 2 forms an expandingmelting zone 14 formed by a first trapezoidal region, and a narrowingmelting zone 16 formed by a second trapezoidal region of wall 2. Thefirst trapezoid forming an expanding melting zone 14 and the secondtrapezoid forming the narrowing melting zone 16 share a common base inthis embodiment, indicated at B, at an intermediate location between themelter inlet 4 and discharge 6. Common base B defines the location ofthe maximum width, W_(M), of melter 100. The primary importance of thesemelting zones is that no 90 degree corners are present in the melterwhere there may be stagnation of molten glass flow.

Another important feature of melter apparatus 100 is the provision ofsubmerged combustion burners 10. In embodiment 100, burners 10 arefloor-mounted burners, illustrated in rows substantially perpendicularto the longitudinal axis, L, of melter 100. In certain embodiments,burners 10 are positioned to emit combustion products into molten glassin the melting zones 14, 16 in a fashion so that the gases penetrate themelt generally perpendicularly to the floor. In other embodiments, oneor more burners 10 may emit combustion products into the melt at anangle (see FIG. 6, angle a) to the floor; this angle α may be more orless than 45 degrees, but in certain embodiments may be 30 degrees, or40 degrees, or 50 degrees, or 60 degrees, or 70 degrees, or 80 degrees.

Melter apparatus in accordance with the present disclosure may alsocomprise one or more wall-mounted submerged combustion burners, asindicated at 25 in FIG. 1, and/or one or more roof-mounted burners 26,as indicated at 26 in FIG. 6. Roof-mounted burners may be useful topre-heat the melter apparatus melting zones 14, 16, and serve asignition sources for one or more submerged combustion burners 10. Melterapparatus having only wall-mounted, submerged-combustion burners arealso considered within the present disclosure. Roof-mounted burners 26may be oxy-fuel burners, but as they are only used in certainsituations, are more likely to be air/fuel burners. Most often theywould be shut-off after pre-heating the melter and/or after starting oneor more submerged combustion burners 10. In certain embodiments, allsubmerged combustion burners 10 are oxy/fuel burners (where “oxy” meansoxygen, or oxygen-enriched air, as described earlier), but this is notnecessarily so in all embodiments; some or all of the submergedcombustion burners may be air/fuel burners. Furthermore, heating may besupplemented by electrical heating in certain embodiments, in certainmelter zones.

FIGS. 2-5 illustrate further embodiments and features of melterapparatus of this disclosure. Embodiment 200 of FIG. 2 illustrates thatwall 20 may have a free-flowing form, devoid of angles. Embodiment 300of FIG. 3 illustrates that wall 320 may be configured so thatintermediate location 12 may comprise an intermediate region of melter300 having constant width, extending from a first trapezoidal region 14to the beginning of the narrowing melting region 160. Narrowing meltingregion 160 in embodiment 300 has alternating narrowing and expandingregions, formed by wall sections 321, 322, although it has a narrowingeffect overall leading to discharge 6. Embodiment 400 of FIG. 4comprises a narrowing melting zone comprising a first narrowing sectionformed by wall sections 420A and 420B which lead to a narrow channelformed by wall sections 421A and 421B, and then a short expanding zoneformed by wall sections 422A and 422B, and finally narrowing down againto discharge 6. Embodiment 400 may provide a final melt mixing orretention zone between wall sections 422A and 422B, which mayadvantageous in certain embodiments, for example when colorants areadded to the melt. Embodiment 500 of FIG. 5 illustrates an embodimentsimilar to embodiment 100 of FIG. 1, except that wall 520 forms anintermediate melting zone 120 of constant width.

FIG. 6 is a side sectional view of the melter of FIG. 1, and illustratesa charge of batch material 15 being fed into melter inlet 4 throughfeeder 5. Three floor-mounted submerged combustion burners areindicated, 10A, 10B, and 10C. FIG. 6 also illustrates angles α and β,where angle α is defined as an angle between floor-mounted burner 10Ccentral axis 50 and horizontal 52, and angle β is defined as the anglebetween horizontal and a line 54 through the floor of the decreasingdepth region of the melter. Values for angle α were mentioned earlier.Angle β may range from about 0 degrees to about 90 degrees, or fromabout 0 degrees to about 60 degrees. [0-90 degrees covers full range offlat bottom to vertical end wall] As angle β is decreased, allowablevalues for angle α may increase, all other factors being equal. Whenangle β is large, say for example 45 degrees or larger, if angle α istoo small, for example 45 degrees or less, unacceptable refractory wearmay occur near or on the inclined region of floor 8, potentiallyaccompanied by lesser quality glass melt, as the refractory materialbecomes part of the melt. It should also be noted that certain melterembodiments may include one or more oxy-fuel and/or air-fuel burnersmounted in the inclined floor region, or wall 2 of the inclined floorregion.

FIG. 7 is a perspective view of a portion of a melter, illustrating twoembodiments of cooled panels useful in melter apparatus of the presentdisclosure. Also illustrated in FIG. 7 is a portion of melter floor 8,and three floor-mounted burners 10. A first cooled-panel 130 isliquid-cooled, having one or more conduits or tubing 131 therein,supplied with liquid through conduit 132, with another conduit 133discharging warmed liquid, routing heat transferred from inside themelter to the liquid away from the melter. Liquid-cooled panel 130 asillustrated also includes a thin refractory liner 135, which minimizesheat losses from the melter, but allows formation of a thin frozen glassshell to form on the surfaces and prevent any refractory wear andassociated glass contamination. Another cooled panel 140 is illustrated,in this case an air-cooled panel, comprising a conduit 142 that has afirst, small diameter section 144, and a large diameter section 146.Warmed air transverses conduit 142 in the direction of the curved arrow.Conduit section 146 is larger in diameter to accommodate expansion ofthe air as it warms. Air-cooled panels such as illustrated in FIG. 7 aredescribed more fully in U.S. Pat. No. 6,244,197, which is incorporatedherein by reference.

In operation of melter apparatus of this disclosure illustratedschematically shown in FIG. 1, feed material, such as E-glass batch(melts at about 1400° C.), insulation glass batch (melts at about 1200°C.), or scrap in the form of glass fiber mat and/or insulation havinghigh organic binder content, glass cullet, and the like, is fed to themelter through a chute 5 and melter inlet 4. One or more submergedcombustion burners 10 are fired to melt the feed materials and tomaintain a molten glass melt in regions 14 and 16. Molten glass movestoward discharge outlet 6, and is discharged from the melter. Combustionproduct gases (flue gases) exit through exit duct 60, or may be routedto heat recovery apparatus, as discussed herein. If oxy/fuel combustionis employed in some or all burners, the general principle is to operatecombustion in the burners in a manner that replaces some of the air witha separate source of oxygen. The overall combustion ratio may notchange. The process of combining fuel and oxygen-enriched oxidant willoccur in the burner combustion chamber (in burners having combustionchambers) and/or shortly after leaving the combustion chamber.Importantly, the throughput of melter apparatus described in the presentdisclosure may behave throughput of 2 ft² per short ton per day (2ft²/stpd) or less, and in some embodiments 0.5 ft²/stpd or less. This isat least twice 2×, in certain embodiments ten times 10× the throughputof conventional melter apparatus.

Melter apparatus described in accordance with the present disclosure maybe constructed using only refractory cooled panels, and a thinrefractory lining, as discussed herein. The thin refractory coating maybe 1 centimeter, 2 centimeters, 3 centimeters or more in thickness,however, greater thickness may entail more expense without resultantgreater benefit. The refractory lining may be one or multiple layers.Alternatively, melters described herein may be constructed using castconcretes such as disclosed in U.S. Pat. No. 4,323,718. The thinrefractory linings discussed herein may comprise materials described inthis 718 patent, which is incorporated herein by reference. Two castconcrete layers are described in the 718 patent, the first being ahydraulically setting insulating composition (for example, that knownunder the trade designation CASTABLE BLOC-MIX-G, a product ofFleischmann Company, Frankfurt/Main, Federal Republic of Germany). Thiscomposition may be poured in a form of a wall section of desiredthickness, for example a layer 5 cm thick, or 10 cm, or greater. Theinsulating composition may be, for example, hydraulically settingcomposition of 6 to 10 weight % Al₂O₃, 32 to 38 weight % SiO₂, 15 to 20weight % MgO, 30 to 35 weight % CaO, and 40 to 200 weight % mixingwater. This material is allowed to set, followed by over a period of 8to 14 hours at 20° C. Next, a second layer of a hydraulically settingrefractory casting composition (such as that known under the tradedesignation RAPID BLOCK RG 158, a product of Fleischmann company,Frankfurt/Main, Federal Republic of Germany) may be applied thereonto.This refractory concrete may be applied with the use of a hydraulicallysetting composition of 50 to 85 weight % Al₂O₃, 5 to 8 weight % SiO₂,and 10 to 20 weight % mixing water. This latter layer is exposed forabout 24 hours to the action of hot air of about 70 to 80° C. Othersuitable materials for the refractory cooled panels, melter refractoryliners, and refractory block burners (if used) are fused zirconia(ZrO₂), fused cast AZS (alumina-zirconia-silica), rebonded AZS, or fusedcast alumina (Al₂O₃). The choice of a particular material is dictatedamong other parameters by the melter geometry and type of glass to beproduced.

Burners useful in the melter apparatus described herein include thosedescribed in U.S. Pat. Nos. 4,539,034; 3,170,781; 3,237,929; 3,260,587;3,606,825; 3,627,504; 3,738,792; and 3,764,287; and 7,273,583, all ofwhich are incorporated herein by reference in their entirety. One usefulburner, for example, is described in the 583 patent as comprising amethod and apparatus providing heat energy to a bath of molten materialand simultaneously creating a well-mixed molten material. The burnerfunctions by firing a burning gaseous or liquid fuel-oxidant mixtureinto a volume of molten material. The burners described in the 583patent provide a stable flame at the point of injection of thefuel-oxidant mixture into the melt to prevent the formation of frozenmelt downstream as well as to prevent any resultant explosivecombustion; constant, reliable, and rapid ignition of the fuel-oxidantmixture such that the mixture burns quickly inside the molten materialand releases the heat of combustion into the melt; and completion of thecombustion process in bubbles rising to the surface of the melt. In oneembodiment, the burners described in the 583 patent comprises an innerfluid supply tube having a first fluid inlet end and a first fluidoutlet end and an outer fluid supply tube having a second fluid inletend and a second fluid outlet end coaxially disposed around the innerfluid supply tube and forming an annular space between the inner fluidsupply tube and the outer fluid supply tube. A burner nozzle isconnected to the first fluid outlet end of the inner fluid supply tube.The outer fluid supply tube is arranged such that the second fluidoutlet end extends beyond the first fluid outlet end, creating, ineffect, a combustion space or chamber bounded by the outlet to theburner nozzle and the extended portion of the outer fluid supply tube.The burner nozzle is sized with an outside diameter corresponding to theinside diameter of the outer fluid supply tube and forms a centralizedopening in fluid communication with the inner fluid supply tube and atleast one peripheral longitudinally oriented opening in fluidcommunication with the annular space between the inner and outer fluidsupply tubes. In certain embodiments, a longitudinally adjustable rod isdisposed within the inner fluid supply tube having one end proximate thefirst fluid outlet end. As the adjustable rod is moved within the innerfluid supply tube, the flow characteristics of fluid through the innerfluid supply tube are modified. A cylindrical flame stabilizer elementis attached to the second fluid outlet end. The stable flame is achievedby supplying oxidant to the combustion chamber through one or more ofthe openings located on the periphery of the burner nozzle, supplyingfuel through the centralized opening of the burner nozzle, andcontrolling the development of a self-controlled flow disturbance zoneby freezing melt on the top of the cylindrical flame stabilizer element.The location of the injection point for the fuel-oxidant mixture belowthe surface of the melting material enhances mixing of the componentsbeing melted and increases homogeneity of the melt. Thermal NO_(x)emissions are greatly reduced due to the lower flame temperaturesresulting from the melt-quenched flame and further due to insulation ofthe high temperature flame from the atmosphere. A cap which may beprovided with a port arrangement having a central port surrounded by aplurality of ports. Typically, the oxidizing gas is provided through thecentral port and the fuel gas through the surrounding ports, but theopposite arrangement is also feasible. In certain embodiments employingoxygen-hydrogen combustion the oxygen is fed through the central portand the hydrogen through the surrounding ports. The central port issupplied from a central conduit. A larger conduit surrounds the centralconduit so as to create an annular space therebetween through which thesurrounding ports are supplied. Surrounding both conduits is a coolingjacket establishing an annular space between the outer conduit and thejacket through which cooling medium such as water may be circulated topreserve the burner in the high temperature environment. The annularspace for the cooling medium may be provided with partitions (not shown)to create a flow path for the cooling medium in which the cooling mediumcirculates from an inlet, to the vicinity of the end cap, and backtoward an outlet. In some submerged combustion arrangements combustionis carried out within the burner and the exhaust gases are injected intothe melt. In other arrangements, using the type of burner shown in the034 patent, is to inject both the fuel and oxidant into the melt and topermit combustion to take place within the melt. In this manner, theenergy released by the combustion passes directly to the moltenmaterial. Additionally, by providing for combustion outside the burner,the conditions to which the burner is subjected are less severe, therebylessening durability requirements.

The term “fuel”, according to this invention, means a combustiblecomposition comprising a major portion of, for example, methane, naturalgas, liquefied natural gas, propane, atomized oil or the like (either ingaseous or liquid form). Fuels useful in the invention may compriseminor amounts of non-fuels therein, including oxidants, for purposessuch as premixing the fuel with the oxidant, or atomizing liquid fuels.

The total quantities of fuel and oxidant used by the combustion systemare such that the flow of oxygen may range from about 0.9 to about 1.2of the theoretical stoichiometric flow of oxygen necessary to obtain thecomplete combustion of the fuel flow. Another expression of thisstatement is that the combustion ratio is between 0.9 and 1.2. Incertain embodiments, the equivalent fuel content of the feed materialmust be taken into account. For example, organic binders in glass fibermat scrap materials will increase the oxidant requirement above thatrequired strictly for fuel being combusted. In consideration of theseembodiments, the combustion ratio may be increased above 1.2, forexample to 1.5, or to 2, or 2.5, or even higher, depending on theorganic content of the feed materials. [issue here could be includingthe fuel content of any batch material, i.e. binder on scrap . . . whichwill result in lower NG flows but higher Oxygen flows to oxidize thebinder. i.e., for mat scrap trial oxygen to NG was about double asbinder acted as a fuel source.

The velocity of the fuel gas in the various burners depends on theburner geometry used, but generally is at least about 15 m/s. The upperlimit of fuel velocity depends primarily on the desired mixing of themelt in the melter apparatus, melter geometry, and the geometry of theburner; if the fuel velocity is too low, the flame temperature may betoo low, providing inadequate melting, which is not desired, and if thefuel flow is too high, flame might impinge on the melter floor, roof orwall, and/or heat will be wasted, which is also not desired.

In certain embodiments of the invention it may be desired to implementheat recovery. In embodiments of the invention employing a heat transferfluid for heat recovery, it is possible for a hot intermediate heattransfer fluid to transfer heat to the oxidant or the fuel eitherindirectly by transferring heat through the walls of a heat exchanger,or a portion of the hot intermediate fluid could exchange heat directlyby mixing with the oxidant or the fuel. In most cases, the heat transferwill be more economical and safer if the heat transfer is indirect, inother words by use of a heat exchanger where the intermediate fluid doesnot mix with the oxidant or the fuel, but it is important to note thatboth means of exchanging heat are contemplated. Furthermore, theintermediate fluid could be heated by the hot flue gases by either ofthe two mechanisms just mentioned.

In certain embodiments employing heat recovery, the primary means fortransferring heat may comprise one or more heat exchangers selected fromthe group consisting of ceramic heat exchangers, known in the industryas ceramic recuperators, and metallic heat exchangers further referredto as metallic recuperators. Apparatus and methods in accordance withthe present disclosure include those wherein the primary means fortransferring heat are double shell radiation recuperators. Preheatermeans useful in apparatus and methods described herein may comprise heatexchangers selected from ceramic heat exchangers, metallic heatexchangers, regenerative means alternatively heated by the flow of hotintermediate fluid and cooled by the flow of oxidant or fuel that isheated thereby, and combinations thereof. In the case of regenerativemeans alternately heated by the flow of hot intermediate fluid andcooled by the flow of oxidant or fuel, there may be present two vesselscontaining an inert media, such as ceramic balls or pebbles. One vesselis used in a regeneration mode, wherein the ceramic balls, pebbles orother inert media are heated by hot intermediate fluid, while the otheris used during an operational mode to contact the fuel or oxidant inorder to transfer heat from the hot media to the fuel or oxidant, as thecase might be. The flow to the vessels is then switched at anappropriate time.

Although only a few exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel apparatus andprocesses described herein. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims. In the claims, no clauses are intended to be inthe means-plus-function format allowed by 35 U.S.C. §112, paragraph 6unless “means for” is explicitly recited together with an associatedfunction. “Means for” clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents, but also equivalent structures.

1. A melter apparatus comprising: a) a floor and a ceiling; b) asubstantially vertical wall connecting the floor and ceiling at aperimeter of the floor and ceiling, a melting zone being defined by thefloor, ceiling and wall, the melting zone having a feed inlet and amolten glass outlet positioned at opposing ends of the melting zone, themelting zone comprising an expanding zone beginning at the inlet andextending to an intermediate location relative to the opposing ends, anda narrowing zone extending from the intermediate location to the outlet;and c) a plurality of burners, at least some of which are positioned todirect combustion products into the melting zone under a level of moltenglass in the zone.
 2. The melter apparatus of claim 1 wherein theintermediate location is positioned where the melting zone has a maximumwidth W_(M).
 3. The melter apparatus of claim 1 wherein at least some ofthe wall comprises fluid-cooled refractory panels.
 4. The melterapparatus of claim 3 wherein the fluid-cooled panels are liquid-cooledpanels comprising one or more passages for flow of a liquid into and outof the passages.
 5. The melter apparatus of claim 1 wherein the meltingzone has a plan view shape defined by first and second trapezoidssharing a common base positioned at the intermediate location andsubstantially perpendicular to a longitudinal axis of the melter, thefirst trapezoid having a side parallel to the base and positioned at theinlet, the second trapezoid having a side parallel to the base andpositioned at the outlet.
 6. The melter apparatus of claim 1 wherein atleast some of the burners are floor-mounted and positioned in one ormore parallel rows substantially perpendicular to a longitudinal axis ofthe melter.
 7. The melter apparatus of claim 1 wherein the 6 wherein thenumber of burners in each row is proportional to width of the melter. 8.The melter apparatus of claim 1 wherein depth of the melter decreases aswidth of the melter in the narrowing zone decreases.
 9. The melterapparatus of claim 1 wherein the intermediate location comprises aconstant width zone positioned between the expanding zone and thenarrowing zone.
 10. The melter apparatus of claim 1 wherein at leastsome of the burners are oxy-fuel burners.
 11. The melter apparatus ofclaim 1 having a throughput of 2 ft²/stpd or less.
 12. The melterapparatus of claim 11 having a throughput of 0.5 ft²/stpd or less. 13.The melter apparatus of claim 12 wherein the melter wall comprises allfluid-cooled panels, the wall comprising a refractory liner at leastbetween the panels and the molten glass.
 14. The melter apparatus ofclaim 1 wherein the wall in the expanding zone and the narrowing zone isnon-linear.
 15. The melter apparatus process of claim 3 wherein thepanels are cooled by a heat transfer fluid selected from the groupconsisting of gaseous, liquid, or combinations of gaseous and liquidcompositions that functions or is capable of being modified to functionas a heat transfer fluid.
 16. The melter apparatus of claim 15 whereinthe gaseous heat transfer fluids are selected from the group consistingof ambient air, treated air, inert inorganic gases, inert organic gases,and mixtures of inert gases with small portions of non-inert gases, andwherein the liquid heat transfer fluids are selected from the groupconsisting of inert liquids which may be organic, inorganic, or somecombination thereof.
 17. A melter apparatus comprising: a) a floor and aceiling; b) a substantially vertical wall connecting the floor andceiling at a perimeter of the floor and ceiling, a melting zone beingdefined by the floor, ceiling and wall, the melting zone having a feedinlet and a molten glass outlet positioned at opposing ends of themelting zone, the melting zone comprising an expanding zone beginning atthe inlet and extending to an intermediate location relative to theopposing ends, and a narrowing zone extending from the intermediatelocation to the outlet, wherein at least some of the wall comprisesfluid-cooled refractory panels; and c) a plurality of burners, at leastsome of which are positioned to direct combustion products into themelting zone under a level of molten glass in the zone.
 18. Theapparatus of claim 17 wherein at least some of the burners arefloor-mounted and positioned in one or more parallel rows substantiallyperpendicular to a longitudinal axis of the melter.
 19. The apparatus ofclaim 17 having a throughput of 2 ft²/stpd or less.
 20. A processcomprising: a) feeding at least one partially vitrifiable material intoa feed inlet of a melting zone of a refractory melter apparatuscomprising a floor, a ceiling, and a substantially vertical wallconnecting the floor and ceiling at a perimeter of the floor andceiling, the melting zone comprising an expanding zone beginning at theinlet and extending to an intermediate location relative to opposingends of the melter, and a narrowing zone extending from the intermediatelocation to a molten glass outlet; b) heating the at least one partiallyvitrifiable material with at least one burner directing combustionproducts into the melting zone under a level of the molten glass in thezone; and c) discharging molten glass from a molten glass outletpositioned at an end of the melting zone opposite the inlet.
 21. Theprocess of claim 20 comprising discharging at least 0.5 short tons perday per square foot of melter floor.
 22. The process of claim 20comprising discharging at least 2 short tons per day per square foot ofmelter floor.
 23. The process of claim 20 comprising cooling the wall bythe wall comprising cooled refractory panels and directing a heattransfer fluid through the panels.
 24. The process of claim 20 whereinthe heating comprises directing combustion products into the meltingzone under a level of the molten glass in the zone employing two or morefloor-mounted burners.
 25. The process of claim 24 comprising directingcombustion products into the melting zone under a level of the moltenglass in the zone employing two or more rows of floor-mounted burnersarranged substantially perpendicular to a longitudinal axis of themelter.
 26. The process of claim 23 comprising decreasing depth of themolten glass as it moves from the intermediate location to the melteroutlet.
 27. A process comprising: a) feeding at least one partiallyvitrifiable material into a feed inlet of a melting zone of a refractorymelter apparatus comprising a floor, a ceiling, and a substantiallyvertical wall connecting the floor and ceiling at a perimeter of thefloor and ceiling, the melting zone comprising an expanding zonebeginning at the inlet and extending to an intermediate locationrelative to opposing ends of the melter, and a narrowing zone extendingfrom the intermediate location to a molten glass outlet; b) heating theat least one partially vitrifiable material with at least one burnerdirecting combustion products into the melting zone under a level of themolten glass in the zone; c) cooling the wall by the wall comprisingcooled refractory panels and directing a heat transfer fluid through thepanels; and d) discharging molten glass from a molten glass outletpositioned at an end of the melting zone opposite the inlet.
 28. Theprocess of claim 27 comprising discharging at least 0.5 short tons perday per square foot of melter floor.
 29. The process of claim 27comprising discharging at least 2 short tons per day per square foot ofmelter floor.
 30. The process of claim 27 wherein the heating comprisesdirecting combustion products into the melting zone under a level of themolten glass in the zone employing two or more floor-mounted burners.31. The process of claim 30 comprising directing combustion productsinto the melting zone under a level of the molten glass in the zoneemploying two or more rows of floor-mounted burners arrangedsubstantially perpendicular to a longitudinal axis of the melter
 32. Theprocess of claim 27 comprising decreasing depth of the molten glass asit moves from the intermediate location to the melter outlet.